1. Field of the Invention
The present invention relates to cooling apparatuses and in particular to cooling apparatuses for cooling an object by a plurality of fans.
2. Description of the Related Art
On an electronic communication apparatus, a countermeasure for the thermal stress (overheating) of electronic parts is very important not only in an aspect of preventing breakdown but also in an aspect of fire protection.
A cooling apparatus that utilizes a fan, which is the most used countermeasure for thermal stress at the present time, is very effective from ease of use and cost perspectives. Accordingly, it seems that a cooling apparatus utilizing a fan will continue to be the most used for the present.
On the other hand, high performance of communication apparatuses realized by current progress such as improvements of capacity and speed causes an increase in consumption of electric power. In addition, high-density mounting or miniaturization causes an increase of thermal stress on electronic parts.
Under such circumstances, the above cooling apparatus is even more indispensable as a cooling means. Here, it is important how to use a plurality of fans systematically as well as to make the fans high-performance. In addition, it is also important to improve the reliability of the cooling apparatuses and to decrease the costs.
However, a countermeasure to increase power of the fans is adopted in conventional designs of cooling systems for communication apparatuses. A characteristic and a reliability to withstand maximum calorific value (heat load) of the communication apparatuses are used in the selection of the fans in the above designs. Therefore, a plurality of fans selected on the basis of the characteristic and the reliability regarding heat load are used in the cooling system.
Then, in conventional cooling systems, excess speed of the fan is common since the fan is always driven under a maximum-power state regardless of the current heat load on the communication apparatus.
On the other hand, a conventional way to improve the cooling ability by increasing the speed of the fan causes various problems and has a limit for satisfying a requirement to improve the cooling performance in communication apparatuses incorporating recent technology innovations.
Namely, increased fan speed causes noise and sometimes breaks the limit of international standards. In addition, since fans are selected on the basis of maximum heat load of the communication apparatus and driven excessively under some heat load conditions, the reliability of the fans is due to the fan reaching a higher speed earlier in its life.
On the other hand, the decrease of air resistance to airflow is important for the efficient cooling operation of the fan.
FIG. 1 is a diagram showing a configuration of a conventional cooling system with heat shielding boards 71. It is noted that FIG. 1(a) is a front view of the cooling system and FIG. 1(b) is a side view thereof. As shown in FIG. 1, the fans 70a, 70b, 70c are arranged above the first, the second, and the third objects of cooling 72, 73, 74 respectively. Hereupon, the cooling system includes the first cooling apparatus with the fan 70a, the second cooling apparatus with the fan 70b, and the third cooling apparatus with the fan 70c. In addition, the system includes heat-shielding boards 71 between the adjacent cooling apparatuses.
The heat shielding boards 71 are used mainly to shield an object from the heat generated by another object. Thus, the cooling ability of each cooling apparatus can be kept independent from one another by the heat shielding boards 71.
However, the direction of the airflow, as indicated by the arrow in the FIG. 1, needs to be changed by 90xc2x0. As the result, the heat shielding boards 71 need to have a height of more than 10 centimeters to effect cooling efficiently and to reduce noise of the cooling. Furthermore, the number of the heat shielding boards 71 increases according to the increasing number of the cooling apparatuses. Therefore, there is a problem that the cooling system becomes larger than desired.
It is a general object of the present invention to provide a novel and useful cooling apparatus and a system with the apparatuses wherein the foregoing problems are eliminated.
A more specific object of the present invention is to provide a cooling apparatus having a plurality of fans and a system with the apparatuses for realizing improvement of cooling reliability and efficiency.
The above objects of the present invention are achieved by a cooling apparatus including a plurality of fan units each having a fan, a plurality of temperature sensors detecting the temperature of an object being cooled by the fan units, and a control portion deciding the speed of the fan according to the temperature detected by the temperature sensors in a self-control mode and increasing the speed of at least one of the other fans when the,speed of any one of the fans is lower than a prescribed threshold in a coordinative control mode.
In another aspect of the present invention, the above objects are achieved by a cooling system including a first fan for supplying air to an object, a second fan for exhausting the air that takes heat from the object, being arranged in the opposite direction as the first fan is from the object, and an adjusting portion for adjusting a flow of the air between the first fan and the second fan.
According to the present invention, the cooling apparatus can have a longer life-span by controlling-the speed of the fan according to the temperature detected by the temperature sensor. in a self-control mode. Furthermore, the present invention can efficiently maintain cooling ability by increasing the speed of at least one of the other fans when any one of the fans becomes out of order in a coordinative control mode. In addition, the present invention can make its maintenance easier by enabling changes for a fan unit since each fan is mounted in a fan unit and controlled independently.
According to another aspect of the present invention, the cooling system can drive the fans efficiently and realize a high density mounting of the fans.
Other objects and further features of the present invention will become apparent from the following detailed description when read in conjunction with the attached drawings.